The utility of variable message display signs since such signs allow a user to display combinations of various visual symbols and characters in order to create different messages for communication to observers. Some variable message signs employ rotating members or drums which have a plurality of facets which can be placed in registration with one another to provide a desired message. These facets may contain characters in the form of letters or numerals, or alternatively, can present pectoral or graphic segments which create an overall image.
Another type of variable sign is known as a scroll sign wherein a pair of rollers have a message web wound thereon so that different messages may be scrolled with respect to a view area thereby providing different messages on the exposed portion of the web. The message web may alternatively carry an entire message which is scrolled into position, or be formed as a module so that each scroll module presents a character in the form of a numeral or letter. A plurality of such modules may then be organized so that a wide variety of different messages can be presented. One such example of a scroll module and sign system utilizing this scroll technique is described in U.S. Pat. No. 4,680,883 issued Jul. 21, 1987 to Stadjuhar et al. and owned by the Assignee of the present invention.
A still further type of variable sign wherein a plurality of character displays are provided to present either a letter of numeral characters organized as a message are known as matrix display devices. In such devices, a plurality of signal elements are organized in a matrix and are used to produce either numerals, letters or both, according to command instructions in order that a desired message is displayed. A wide variety of signal elements may be used in such matrix displays. For example, an electromagnetic shutter device is described in U.S. Pat. No. 3,975,728 issued Aug. 17, 1976 to Winrow. In such device, a rotatable element is moved between two positions by electromagnet. In one position, the element corresponds to an "off" state while in the other position corresponds to a "on" state for the associated pixel in the matrix. U.S. Pat. No. 4,040,193 issued Aug. 9, 1977 to Matsuda et al. discloses a shutter type signal element wherein the shutter member is rotated between two position to expose two different colors. U.S. Pat. No. 4,163,332 issued Aug. 7, 1979 to Salam discloses yet another type of shutter device that may be used in a matrix display.
In addition to the above described shutter type matrix devices, it is known to use lighting elements, such as lightbulbs, light emitting diodes or groups of bulbs or diodes to form a pixel for a matrix display. In such devices, no shutter masking is utilized; rather, each individual signal element, whether a lightbulb, diode array or the like, it is selectively powered between the off state and the on state so that the pattern of pixels in the on state generate the desired character. It is also known in such devices to use other types of signal elements, such as liquid crystal displays, magnetic fluid devices, etc. to create a desired character.
Yet other variable signs employ a different type of matrix arranged to produce a numeral, a letter or both. Here, a rectangular perimeter is typically formed of a plurality of character segments, and character segments extend medially between the opposed sides of the rectangular and, if desired, diagonally. By selectively placing desired segments in the "on" state, a selected numeral, or letter (depending upon the character design) can be presented. One example of a numeric display is described in U.S. Pat. No. 4,496,945 issued Jan. 29, 1985 to Stadjuhar et al. and assigned to the Assignee of the present invention. U.S. Pat. No. 3,273,270 issued Sep. 20, 1966 shows a segmented display module using a shutter system to produce numerals or letters. Here again, various types of magnetic or mechanical shutters may be employed, numerous devices such as lightbulb and light emitting diodes may be used, liquid crystal displays employed, or other types of changeable signal elements employed, all as known in the art.
Due to the existence of these known techniques for producing variable displays, it is highly desirable to remotely control the message presented thereon. Thus, for example, a central command station may be able to communicate with distantly located controllers for respective signs in order to demand those controllers to change their associated character displays to a selected message. The display characters, themselves, may be remote from their respective controller such as occurs in a sign that is elevated with the controller therefor being located on the ground surface.
The present invention relates to a control system interfacing such a controller located remotely from its associated character displays. It should be appreciated that the variable message display sign according to the present invention is directed to the control of character displays of the matrix type wherein a plurality of pixels or segments are selectively actuated to form the desired display. This invention may be employed with character displays having signal elements defining the pixels therefore, where such pixel elements or any type known in the art or hereinafter developed and where such signal elements can switch between the on state and off state to display the desired message.